Bottlebrush polymers represent a unique molecular architecture and a modular platform for materials design. However, the properties and self-assembly of bottlebrush polymers remain relatively unexplored, in large part due to the synthetic challenges imposed by the sterically demanding architecture. This thesis describes our work to close this gap, connecting (1) the synthesis of polymers with precisely tailored molecular architectures, (2) the study of fundamental structure-property relationships, and (3) the design of functional materials.
Chapter 1 introduces key concepts related to polymer architecture and block polymer phase behavior. Recent developments in the synthesis and self-assembly of bottlebrush block polymers are highlighted in order to frame the work presented in Chapters 2–6.
Chapter 2 introduces a versatile strategy to design polymer architectures with arbitrary side chain chemistry and connectivity. Simultaneous control over the molecular weight, grafting density, and graft distribution can be achieved via living ring-opening metathesis polymerization (ROMP). Copolymerizing a macromonomer and a small-molecule co-monomer provides access to well-defined polymers spanning the linear, comb, and bottlebrush regimes. This design strategy creates new opportunities for molecular and materials design.
Chapter 3 explores the physical consequences of varying the grafting density and graft distribution in two contexts: block polymer self-assembly and linear rheological properties. The molecular architecture strongly influences packing demands and therefore the conformations of the backbone and side chains. Collectively, these studies represent progress toward a universal model connecting the chemistry and conformations of graft polymers.
Chapter 4 discusses the phase behavior of ABA' and ABC bottlebrush triblock terpolymers. Low-χ interactions between the end blocks promote organization into a unique mixed-domain lamellar morphology, LAMP. X-ray scattering experiments reveal an unusual trend: the domain spacing strongly decreases with increasing total molecular weight. Insights into this behavior provide new opportunities for block polymer design with potential consequences spanning all self-assembling soft materials.
Chapter 5 describes other physical consequences of low-χ block polymer design. The ternary phase diagrams for ABC, ACB, and BAC bottlebrush triblock terpolymers reveal the influences of low-χ A/C interactions, frustration, and the molecular architecture. Potential non-equilibrium effects and crystallization in these bottlebrush polymers will also be discussed.
Chapter 6 describes applications of bottlebrush polymers as functional materials. Self-assembly enables mesoscale structural control over many materials properties, such as reflectivity, conductivity, and modulus. The synthetic methods (Chapter 2) and physical insights (Chapters 3−5) provided in previous chapters illustrate opportunities for materials design. We will discuss AB brush diblock polymers that self-assemble to photonic crystals and ABA brush triblock copolymers in solid polymer electrolytes.</p
